CA1066542A - Lobular socket head fastener with service slot - Google Patents

Abstract

LOBULAR SOCKET HEAD FASTENER
WITH SERVICE SLOT

Abstract of the Disclosure There is disclosed a socket head type fastener which employs in addition to a primary, lobular drive socket, an au-xilliary drive tool engaging means in the form of a service slot for the reception of a screwdriver or similar type driving tool.
The service slot enables the fastener to be removed and rein-stalled by a serviceman in the field, when the specific drive tool sized to mate with the lobular socket is not available.
The socket and service slot combination is of a special design in that said socket is of a multi-lobular configuration designed for engagement by a correspondingly shaped multi-lobular tool, where the respective lobes of each will be in engagement over known surface area portions upon driving of the fastener, as determined by industry standards. The service slot means is provided by a pair of slots which open into the socket through the arcuate wall surfaces of the opposed lobes. The slots are constructed such that the side walls thereof intersect the ar-cuate surface serving to define the flutes and lobes at locations disposed outwardly of the lobe surface portions which are engaged with the drive tool lobes. As such the presence of the service slot does not diminish the socket lobe surface area for resis-tive or driven engagement with the tool lobes.

Description

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Back~round of the Invention The present invention relates to socket h~ d type fasteners and more particularly to a fastener drive arrangement, wherein a multi-lobular socket is provided for engagement by a correspondingly shaped, mating drive tool, with the end face o~ the socket head including an auxil:Liary or service slot thereby adapting the fastener to be driven by a standard tool engaged in said socket, such as a screwdriver or the like.
As will be discussed in greater detail hereinafter, socket head fastenerswith a service slot type of auxilliary drive means are well known in the art. By way of exampLe, in~
vestigation may be had with regard to the following prior art references:
United States Patent No. 2,556,155 Stellin June 5, 1951 United States Patent No. 2,395,476 Givnan Feb. 22, 1946 United States Patent No. 2,359,898 Clark Oct. 10, 1944 `~
United States Patent No. 2,322,509 DeVellier June 22, 19~3 ;~ ~ ;
United States Patent No. 2,173?707 Brown Sept. 19, 1939 ~
United States Patent No. 2,140,449 Brown Dec. 13, 1938 ~-United States Patent No. 1,910,182 Robertson May 23, 1933 United States Patent No. 422,307 Libbey Feb. 25, 1890 -~
United States Patent No. 6~729 Cummings Nov. 9, 1875 British Patent No. 1,027,698 April 27, 1966 ;

These prior art references are concerned mainly with a primary drive socket, which is defined by intersecting planar :
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surfaces to provide either a hex or square drive. The hex or square type of drive system has been found to posses numerous disadvantages due to the relatively sharp corners employed and the attendant low eficiency in the converting of applied tor-que to driving torque. As an additional matter, th e hex and square type of drive socket are subject to higher radial stresses which can result in failure during driving. Accordingly, in recent years lobular type drive systems, such illustrated in Applicant's prior United States Patent No. 3,584,667 have been proved more efficient than the hex or square systems, and have gained industry-wide acceptance.
While lobular type drive arrangements with service slot auxilliary drive means have been proposed, i.e. the Stellin patent noted above, the overall design of these drive systems involve the sacrifice of the efficiency of the primary drive system due to the presence of the slot means. More spe- ~ -cifically, these prior art servic~ slots open into the socket at locations which in effect result in the removal of a volume of material which would normally provide a lobe surface portion 20 against which the drive tool lobes will engage. As such, the ~ -operational characteristi~s of the primary drive system are compromised, viz.,its ability to withstand and transmit torque.
In order to regain the overall strength for primary drive system, the prior art designs normally resort to a deepening of the socket to increase the depth of engagement and surface area in contact.
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In some instances the circumferential wall which defines the socket has been thickened. These changes tend to complicate fabrication of the fastener, as well as the manufacturP of the socket forming tools The present invention, as will be discussed in greater detail hereinafter, provides a lobular type socket with a ser-vice slot designed and located, such that the resulting combin~
ation does not compromise the operational characteristics of the primary drive system. Thus there is no necessity to deepen the main socket, otherwise thicken the circumferential wall defining the socket.
As alluded to above~ lobular type drive systems are widely used. These systems employ lobes which in section in-` clude generally arcuate surface portions. The latter type is `~
contemplated by the present invention. ~rive systems utilizing -;~
arcuate lobes are possessed of certain advantages in that it is -~
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relatively easy to attain mating engagement of a drive tool in ~
the socket. In this regard, industry accepted standards and ;-~ -practices provide for the dimensioning of the drive tool end ~; 20 portion such that same is slightly smaller than the drive socket ~
to facilitate engagement of the respective elements. During ~?`
driving of the fastener, full surface-to-surface engagement of the respective lobe surfaces does not result, due to this di- ~-mensional difference. In fact, it has been found that the lobes will be in engagement only over relatively small surface areas, , ~ .

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as defined by the length of engagement along the abutting surfaces and the depth of engagement of the drive tool in the fastener socketO It should be noted, as is dis-cussed in Applicant's prior Patent No. 3,584,667 that the degree of surface-to-surface engagement obtained with a lobular drive systems is far greater than that achieved with more conventional hex or square systems;
an~ alsa a low drive angle is obtained which results in the efficient conversion of applied torque to driving torque, and reduces the radial stresses which can lead to fracture of the socket wall, The present invention thus provides a socket head type fastener having an elongate shank and enlarged head portion with a multi-lobular drive socket formed therein.
The peripheral wall surface of said lobular socket being provided by a first series of inwardly convex, arcuate wall surfaces and a second series of outwardly concave, arcuate wall surfaces with said surfaces mergingsmoothly to define alternately disposed socket lobes and flutes, with at least two of said flutes being diametrically opposed. The socket is adapted to recieve a drive tool end portion of a corresponding, multi-lobular mating con-figuration , with each lobe on said drive tool end portion being in eng~gement with the socket wall surface o~er a first surface area portion upon the cloc~wise rotation and in engagement with a second, oppositely : - 5 -B

~ 6~542 disposed surface portion of said socket wall surface upon the counterclockwise rotation with said first and second surface area portions being defined primarily by said inwardly convex, arcuate wall surfaces. The astener including auxilliary drive means formed in said head por-tion and including diametrically opposed first and second slot means adapted to cooperate with said socket to j provide for the reception of an alternate drive tool such as a screwdriver or the likeO One of said slot means being assoclated with each said diametrically opposed flute, and opening into said socket through the outwardly .. concave, arcuately curved surfaces serving to define said flutesO Each slot means is defined partially by a pair of sp~ced, generally parallel side wall surfares extending axially from the end face of said head portion and outwardly from said socket, wh~ch side wall surfaces intersecting the outwardly concave, arcuately cur~ed surface of the associate flute at locations spaced along said surface, and disposed radially outward from said first and second surface area portionsof engagementO Thus the existence of said slots does not dimlnish the extent of said surface area portions available for engagement with the lobes on the drive toolO
Description of the Drawings Figure 1 is perspective view illustrating a fastener constructed in a~ ordanre with the present - :
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invention, and the end portion of a drive tool engage-able wi~h said fastenerg Figure 2 is top plan view of the driving head of the fastener illustra~ed in Figure l;
Figure 3 is partial sectional view of a fastener in accordance with the present inVentiQn, and includes a view of the end portion of a drive tool adapted for engagement in the astener socket;
Figure 4 is partial sectional view taken through the driving head of a fastener constructed in accordance with the present invention with the d~ive tool engaged therewith~ with the respective lobes in engagement as would occur during driving o the ~astener in cou~ter~
clockwise direction, :.

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Description of the Illustrated Embodiment The invention will first be described with respect to the structural features of the novel, improved drive system and the mating drive tool illustrated. A detailed discussion of the manner in which these structural features cooperate to `
provide the improved results discussed above, will be had with regard to Fig. 4.
In Fig. 1, there is illustrated a fastener 10 having an elongate shank 12 with an enlarged head portion 14 on one end thereof. The opposite end of the shank 12 may be provided with screw threads 16 of a conventional design or such other structure that may be desired to matingly engage the fastener with a work piece (not shown). The enlarged head portion 14 ` includes primary drive means in the orm of a lobular socket, designated generally 20. A drive tool 22 is also illus~rated, which includes an end portion 24 of a lobular configuration ``
designed for mating engagement in the socket 20.
With reference to Figs. 2-4, the specific des;gn of the socket 20 which provides the primary drive system for the fastener 10 can be seen. In this regard, socket 20 includes an inner peripheral wall surface which may be described as lobular, and is comprised of a plurality of alternating flutes - 30 and lobes 32. The lobes 32 and flutes 30 arc formed by a first series of inwardly concave surfaces 34 and a second series of outwardly convex surfaces 36 which merge smoothly, as ~hown ' ~66~i~2 in Fig. 4. The respective surfaces 34 and 36 extend axially of the socket, as shown in Fig. 2, with the bottom wall 37 of the socket being cone shaped.
With re~erence to Fig. 4, it can be seen that the radius of curvature 40 of the second series of surfaces 36 is considerably smaller than the radius of curvature 42 for the first series of surfaces 34. In the illustrated embodiment the ratios of said dimensions will be on the order of 4 or S-to-l. Accordingly, the angular extent of said first convex series of surfaces 34 is much greater than that of said second series of surfaces 36 with this relationship providing rather substantial, radially inward projecting lobes 32.
The particular design of the socket 20, as illustrated and as discussed above, is essentially that as shown in Appli-cant's prior United States Patent No. 3,584,667. It is intended, however, that the socket 20 as illustrated is but one type of lobular drive socket that can be employed with the present in-vention.
The end portion 24 of the drive tool 22 is of a corresponding, multi-lobular configuration. More specifically, said end portion 24 includes a series of alternating lobes and flutes 50 and 52, respectively, which are of course configured oppositely of those of the socket 20, so as to mate with the opposed lobes and ~lutes 32 and 30 of said socket 20. That is to say, while the surface 34 having the largest radius of cur-vature 42 forms the lobes 32 on the socket well, it is the : !

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1at6~5~2 surfaces with the smaller radius of curvature which provide the lobes 50 on the drive tool end portion.
In accordance with uniform, industry accepted stan-dards and practices, the surfaces which provide the drive tool lobes 50 and flutes 52 are dimensioned to be slightly less than the dimensions o~ the corresponding surfaces of the socket which provide the opposed lobes 32 and flutes 30. This dimensioning practice is uniformly followed by all fastener and tool manu-facturers, and it assures the presence of a slight clearance between the respective parts upon engagement of the tool end portion 24 in the socket 20. The radial clearance which is obtained, and visible in Fig. 4, will of course vary from part to part, depending upon the actual tolerances used in manufacture of the respective parts. T~ard this end, fastener and tool manufacturers have cooperated to develop dimensional standards for the various accepted drive systems, such as the disclosed embodiment marketed under the Trademark TORX.
; Fig. 4 illustrates the condition of engagement of ~`
the respective lobes 32 and 50, upon rotation of the driver in 20 a counter-clockwise direction. It is important to note, that ~;
the respective lobes 32 and 50 will be in engagement only along the surface portions 60, as illustrated in Fig. 4. This results due to the slightly smaller dimensional tolerances held with re- -` spect to the end portion 24, in order to provide the radial -clearance necessary for ease in the obtaining of mating engagement.

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' .~.: .. ., : -~O~:;G542 The area of mutual engagement 60 is disposed radially outward ; of the innermost point on the lobe 32, and with respect to lobe 50, radially inward of the outermost point on said lobe. As an additional point, when the driver 22 is rotated in the op-posite direction, as would be the case in seating of the fas-tener 10, the areas of engagement will be on the opposite sides of the respective lobes 50 and 32, as indicated by reference 60'.
As an additional matter, the head portion 14 may in-clude if desired, a slight countersink 64, as illustrated inFigs. 1 and 2, to further aid in the engagement of the tool and the socket 20. Also, as can be seen in Fig. 2 the upper sur-faces of the lobes 32 on said socket are provided with a taper surface 65 to facilitate further engagement of the end portion 24 in said socket. While the aforementioned taper surface 65 and countersink 64 are desirable, they are of course optional ;~ -features with respect to the present invention.
Attention is now directed to the auxilliary or secon-dary drive means employed in conjunction with the primary drive system provided by the lobular socket 20. In this regard, it will be noted that the lobular design of the socket 20 is such !~`.' `
that at least one pair of flutes 30 are diametrically opposed.
Accordingly, first and second slot means 70 and 72 are ~ormed in the end face of the enlarged head portion 14, which slots ... . .
preferably align radially with the center of curvature for the .

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outward concaved, arcuate surface 36 serving to form the asso-ciated flutes 30. As such, with the tool 22 removed, the slots 70 and 72, in conjunction with the socket 20, provide a space for reception of a secondary drive tool (not shown) in the form of a screwdriver, or the like.
Each said slot is defined by a pair of spaced, ge-nerally parallel side walls 74 and 76, Fig. 4, a tapered or slanted end wall 78, and a planar bottom wall 80 disposed generally perpendicular to said side walls 74 and 76. The side walls 74 and 76 extend axially from the end face 82 of the enlarged head portion 14, and radially inward from the tapered end wall 78 to the outwardly concave, arcuate surfaces 36 which define the associated flute.
Most importantly, said side walls 74 and 76 intersect the arcuate surface 36 at locations 84 and 86, Fig. 4. These locations 84 and 86, are disposed along the surface 36 radially outward of the surface portions of surfaces 36 and 34 which ~`
define the areas of engagement, 60 and 60'. Thus, when the driver 22 is engaged with the socket wall 20, the normal full surface area of the socket lobes 32 are provided for resistive engagement with the lobe 50, even though the auxilliary or service slots 70 and 72 are present. Therefore, as was dis-cussed previously in the introductory portion of the application, the operational characteristics of the primary drive system pro-- .
vided by the socket 20 are not compromised, in any way, by the -:; , .: ~, : - , ~ 5 ~'~

presence of the auxilliary drive means afforded by the slots 70 and 72.
As an additional point, it should be noted that the slots 70 and 72 terminate shortof the outer peripheral wall 90 of the enlarged head portion 14. Accordingly, the resulting wall structure provided by the head portion 14 and slot 20 is circumferentially continuous. This is a significant f~ature, as designs employing slots which extend entirely through the wall structure of the enlarged head, tend to reduce the overall strength of the fastener. More specifically, when the fastener is engaged and is torqued to achieve a tight, clamped engagement with the work piece, the shank 12 is stressed in tension with the enlarged head 14 engaged against the work piece. If the service slots extended entirely through the head, the stresses established upon the enlarged head portion tend to collapse or . j .
otherwise deform the wall structure defining said slots, thereby preclude subsequent engagement of an auxilliary tool therein.
The specific design of the socket 20 as discussed above corresponds to that as illustrated in Applicant's prior patent, and sold under the Trademark TORX. This design, re~
sults in the attainment of a drive angle 92 on the order of -~.
. 10 - 20. In the fas~ener art, the drive angle is defined by a line extending generally along the engaged surfaces 60 and :;
the radial axis or the associated lobe 50. In practice, the lower the drive angle 92, the greater the efficiency of the '';'~ ~

. ~ .. .. ~... . . . ,. - ,, . . ... . . .. ~ ., , ~06G542 drive system, viz. the ratio of applied torque to driving torque transmitted to the fastener. That is to say, the applied torque transmitted from the tool to the fastener can be broken down into a radial vector, which serves no useful function,and a tangential vector, which is the driving torque applied to the fastener. The lower the drive angle 92, the greater the tan-gential vector, and thus the greater the efficiency of the drive system.
Accordingly, when the present invention is employed in conjunction with the specific type of drive system as il-lustrated in the drawings and as described in detail in Appli- ;~
cant's prior patent, certain additional advantages are obtained.
More specifically, since the radial force or torque components are extremely low, the thickness of the wall structure may be reduce therby resulting in a substantial savings of raw ma- I-terial. Further, due to the absence of damaging radial stress ¦
it is possible to have the slots 70 and 72 extend to a point ¦
closely adjacent to the outer peripheral wall surface, without ¦
the danger of weakening the drive head. Accordingly, the range of the size of the tools that can be utilîzed with the auxil-liary drive slots is increased.
While there has been described a preferred embodiment - of the present invention, it should be understood that various modifications or alterations may be employed without departing from the spirit and scope of the invention. More specifically, '~, ~:

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the particular type of lobular socket or auxilliary drive slot utilized may vary from that as illustrated, even though par-ticular advantages follow from the use of the disclosed primary drive system. Therefore, although a preferred embodiment has been illustrated and described, it is to be understood and indeed is intended that various alterations in the detail or dimension may be made without departing from said spirit and scope of the invention, as defined in the claims appended ;
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Claims (6)

The embodiment of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A socket head type fastener having an elongate shank and enlarged head portion formed on one end of said shank, a multi-lobular drive socket formed in said enlarged head portion, with the peripheral wall surface of said lo-bular socket provided by a first series of inwardly convex, arcuate wall surfaces and a second series of outwardly con cave, arcuate wall surfaces with said surfaces merging smoothly to define alternately disposed socket lobes and flutes, and at least two of said flutes being diametrically opposed, said socket being adapted to receive a drive tool end portion of a corresponding, multi-lobular mating confi-guration, with each lobe on said drive tool end portion be-ing in engagement with the socket wall surface over a first surface area portion upon the clockwise rotation of said fastener, and in engagement with a second, oppositely dis-posed surface portion of said socket wall surface upon the counterclockwise rotation of said fastener, with said first and second surface area portions being defined primarily by said inwardly convex, arcuate wall surfaces, and auxilliary drive means formed in said head portion and including dia-metrically opposed first and second slot means adapted to cooperate with said socket to provide for the reception of an alternate drive tool such as a screwdriver or the like, in driving engagement with said fastener, one said slot means being associated with each said diametrically opposed flute, said slot means opening into said socket through the out-wardly concave, arcuately curved surfaces serving to define said flutes, each said slot means being defined partially by a pair of spaced, generally parallel side wall surfaces ex-tending axially from the end face of said head portion and outwardly from said socket, said side wall surfaces inter-secting said outwardly concave, arcuately curved surface of the associate flute at locations spaced along said surface, and disposed radially outward from said first and second sur-face area portions engaged by said drive tool lobes, such that the existence of said slots close not diminish the ex-tent of said surface area portions available for engagement with the lobes on said drive tool.

2. A fastener according to claim 1 wherein each said slot includes an end wall surface disposed inwardly of the outer peripheral surface of said socket, thereby to pro-vide a continuous segment of wall structure about the entire circumference of said socket.

3. A fastener according to claim 1, wherein the radius of curvature of said first series of surfaces is at least twice as great as the radius of curvature of said second series of surfaces such that the arcuate extent of said inwardly extending lobes is materially greater than the arcuate extent of said flutes.

4. A socket head type fastener according to claims 1-3 wherein said shank portion includes a threaded segment thereon.

5. A socket head type fastener according to claims 1-3 wherein each slot includes a planar bottom wall surface which is disposed substantially at right angles to said side wall surfaces and the axis of said socket.

6. A socket head type fastener according to claims 1-3 wherein the depth of said slot means is equal to or less than one-half the depth of said socket flutes.